diff --git a/eobuilder-ctl b/eobuilder-ctl
index 0414c0e..e6cb665 100755
--- a/eobuilder-ctl
+++ b/eobuilder-ctl
@@ -418,18 +418,35 @@ def get_git_project_path(project_reference):
     return os.path.join(settings.GIT_PATH, get_git_project_name(project_reference))
 
 
+def get_git_branch_name(project_reference):
+    git_project_path = get_git_project_path(project_reference)
+    for branch_name in ('main', 'master'):
+        try:
+            subprocess.check_call(['git', 'rev-parse', branch_name],
+                    stdout=subprocess.DEVNULL,
+                    stderr=subprocess.DEVNULL,
+                    cwd=git_project_path)
+        except subprocess.CalledProcessError:
+            continue
+        return branch_name
+    else:
+        raise Exception('failed to determine branch')
+
+
 def setup_git_tree(project_reference, options):
     project_name = get_git_project_name(project_reference)
     git_project_path = get_git_project_path(project_reference)
-    if options.branch.startswith('wip/'):
+    if options.branch and options.branch.startswith('wip/'):
         if os.path.exists(git_project_path):
             shutil.rmtree(git_project_path)
     if os.path.exists(git_project_path):
         existing_tree = True
-        os.chdir(git_project_path)
+        branch_name = get_git_branch_name(project_reference)
         try:
-            subprocess.check_call(['git', 'checkout', '--quiet', options.branch])
-            subprocess.check_call(['git', 'reset', '--hard', 'origin/%s' % options.branch])
+            subprocess.check_call(['git', 'checkout', '--quiet', branch_name],
+                    cwd=git_project_path)
+            subprocess.check_call(['git', 'reset', '--hard', 'origin/%s' % branch_name],
+                    cwd=git_project_path)
         except subprocess.CalledProcessError as e:
             print(e, file=sys.stderr)
             shutil.rmtree(git_project_path)
@@ -446,10 +463,14 @@ def setup_git_tree(project_reference, options):
             else:
                 project_url = project_reference
             call("git clone %s" % project_url)
+        branch_name = get_git_branch_name(project_reference)
+
+    if not options.branch:
+        options.branch = branch_name
 
     os.chdir(git_project_path)
     try:
-        subprocess.check_call(['git', 'checkout', '--quiet', options.branch])
+        subprocess.check_call(['git', 'checkout', '--quiet', branch_name])
         subprocess.check_call(['git', 'pull'])
         subprocess.check_call(['git', 'submodule', 'init'])
         subprocess.check_call(['git', 'submodule', 'update'])
@@ -473,7 +494,7 @@ def main():
     project_reference = args[0]
     git_project_path = get_git_project_path(project_reference)
     atexit.register(clean_git_on_exit, git_project_path)
-    if options.branch.startswith('origin/'):
+    if options.branch and options.branch.startswith('origin/'):
         # normalize without origin/
         options.branch = options.branch[len('origin/'):]
     existing_tree = os.path.exists(git_project_path)
@@ -496,11 +517,12 @@ def main():
     # compare revision between last build and now to determine if something is really new
     new = 1
     current_revision = output("git rev-parse HEAD", True).strip()
+    branch_name = get_git_branch_name(project_reference)
     last_branch_revision_file_path = os.path.join(
         project['lock_path'],
         "%s_%s.last_revision" % (
             project['name'],
-            options.branch.replace('/', '_')))
+            branch_name.replace('/', '_')))
     try:
         with open(last_branch_revision_file_path) as f:
             last_branch_revision = f.read().strip()
@@ -516,7 +538,7 @@ def main():
 
     for dist in options.distrib:
         os.chdir(git_project_path)
-        call("git checkout --quiet %s" % options.branch)
+        call("git checkout --quiet %s" % branch_name)
         package = prepare_build(dist, project, options, new)
         if package:
             for arch in options.architectures:
@@ -527,13 +549,13 @@ def main():
                 "%s_%s_%s_%s.build" % (project['name'],
                     package['version'],
                     package['repository'],
-                    options.branch.replace('/', '_'))
+                    branch_name.replace('/', '_'))
                 ))
 
             last_version_file = os.path.join(project['lock_path'],
                     "%s_%s_%s.last_version" % (project['name'],
                                 package['repository'],
-                                options.branch.replace('/', '_'))
+                                branch_name.replace('/', '_'))
                     )
             with open(last_version_file, 'w+') as f:
                 f.write(package['version'])
diff --git a/eobuilder/cmdline.py b/eobuilder/cmdline.py
index 63334a6..6e50240 100644
--- a/eobuilder/cmdline.py
+++ b/eobuilder/cmdline.py
@@ -47,8 +47,7 @@ def parse_cmdline():
     parser.add_option("-b", "--branch",
             action="store", type="string",
             dest="branch", metavar='NAME',
-            default="master",
-            help="branch to build (Default: master)")
+            help="branch to build (Default: main, or master)")
     parser.add_option("--epoch",
             action="store", type="string",
             dest="epoch", metavar='EPOCH',